1. Field of the Invention
The invention relates to a grinding media for the fragmentation and grinding of ores, rock and earth mass and other inert materials in drum and other types of mills, and it finds application in ore mining, construction and other industrial branches.
2. Description of the Prior Art
Widely known and used in practice is grinding media for drum mills with a spheroidal form. A disadvantage of the spheroidal grinding media is the low productivity of the mills, operating with such media, because their form does not allow good compaction of the working space, and the lack of edges extends the time for breaking of the grinded material and reduces the effectiveness.
From the prior art, a grinding media in the form of a tetrahedron with smooth or slightly rounded walls at their ends and rounded edges and tips [DE 440198/1927] is also known. This grinding media is more effective from the spheroidal one because it allows for a better compaction of the working space. A drawback of this grinding media is that its form is difficult to be manufactured by stamping, rolling or founding—the main methods for the manufacturing of mass articles of this kind. This leads to a big increase of manufacturing costs of grinding media and reduces the effectiveness from their usage. Another drawback of this grinding media proceeds from its geometric form—flat surrounding walls—its rolling in the mill during the working process is difficult, and the contact surface between the grinding media and the mill's walls is rather small.
From the prior art, a grinding media with the form of “Reuleaux triangle” with rounded edges and tips, obtained from the crossing of four spheres, the centers of each one lie on the top of the surface of the others and appearing as tips of regular tetrahedron and the radii of the spheres are equal to the regular tetrahedron's edge [RU1 388088/1985] is also known. This grinding media is more effective than those with spheroidal or pyramidal form, as it allows better compaction of the working space and at the same time provides a bigger contact area between the grinding media and the mill's wall at equal mass. An essential drawback of this grinding media is that its manufacturing is a complicated and labour-consuming process, which makes the grinding media much more expensive and reduces the profitability from its use in the grinding process.
A cubic shape grinding body with flat sides and whose edges and tips are roundly beveled is also known—[US 1 431 475/1922]. That grinding body was also highly non-technological to produce because of which it had not found wide application.
A spheroidal tetrahedron shape grinding body is also known, of which only three edges coming of the same tip are rounded and the remaining edges and tips are not rounded [RU 2 305 597/2007]. The surfaces of those three rounded edges are formed by the rotation of the arcs of the edges around the chords, connecting two tips. Those three edges of the tetrahedron have a cross-section similar to a circle and their cross-sections are variable along their lengths. That suggested body is known in geometry as Meissner Tetrahedron. That grinding body is exceptionally difficult and expensive to produce, and the additionally rounded edges with the described shape and variable cross-section would prevent the sliding of the bodies at each other, which in turn would make the grinding of ore materials impossible.
In another patent [FR 811 408/1937] a grinding body of shape similar to the above mentioned patent [DE 440 198/1927] is discussed. A general characteristic of the described body of tetrahedron shape with flat or slightly rounded faces, as well as of spheroidal tetrahedron shape, whose faces are part of a sphere, is its extremely difficult and expensive, even practically impossible mass production, which is a requirement for the grinding bodies.
Cubes, even with round beveled tips and edges, are equally inapplicable for mass production.